Water-Insoluble Drug Formulation

Ron Liu, Ron Liu

• Publisher: CRC Press
• Year: 2018
• ISBN:
  9781351646826
• Edition: 3
• Topic: Medicine
• Subtopic: Pharmacology

Properties and Formulation: From Theory to Real-World Application

Scientists have attributed more than 40 percent of the failures in new drug development to poor biopharmaceutical properties, particularly water insolubility. Issues surrounding water insolubility can postpone or completely derail important new drug development. Even the much-needed reformulation of currently marketed products can be significantly affected by these challenges. More recently it was reported that the percentage increased to 90% for the candidates of new chemical entities in the discovery stage and 75% for compounds under development.

In the most comprehensive resource on the topic, this third edition of Water-Insoluble Drug Formulation brings together a distinguished team of experts to provide the scientific background and step-by-step guidance needed to deal with solubility issues in drug development. Twenty-three chapters systematically describe the detailed discussion on solubility theories, solubility prediction models, the aspects of preformulation, biopharmaceutics, pharmacokinetics, regulatory, and discovery support of water-insoluble drugs to various techniques used in developing delivery systems for water-insoluble drugs. This book includes more than 15 water-insoluble drug delivery systems or technologies, illustrated with case studies and featuring oral and parenteral applications. Highlighting the most current information and data available, this seminal volume reflects the significant progress that has been made in nearly all aspects of this field.

The aim of this book is to provide a handy reference for pharmaceutical scientists in the handling of formulation issues related to water-insoluble drugs. In addition, this book may be useful to pharmacy and chemistry undergraduate students and pharmaceutical and biopharmaceutical graduate students to enhance their knowledge in the techniques of drug solubilization and dissolution enhancement.

1	Introduction Rong (Ron) Liu

“These new compounds, like rocks, never dissolve in water.” It sounds so familiar to you, does it not? Product development scientists often encounter significant difficulties in solving the problem of poor water solubility of drug candidates in the development of pharmaceutical dosage forms (Sweetana and Akers, 1996; Yamashita and Furubayashi, 1998; Willmann et al., 2004; Di et al., 2006). Poor drug-like properties of lead compounds led to ineffective absorption in the site of administration, which has been designated as an important part of the high clinical failure due to poor pharmacokinetics (Caldwell et al., 2001; Kerns and Di, 2003; Hartmann et al., 2006). However, these kinds of compounds represent an increasing proportion of newly discovered drug candidates. It is commonly recognized in the pharmaceutical industry that on average more than 40% of newly discovered drug candidates are poorly water soluble. Recently, it was reported that the percentage could be as high as 90% for new chemical entities (Kalepu and Nekkanti, 2015) and 75% for compounds under development (Rodriguez-Aller et al., 2015). As a matter of fact, poorly soluble compounds represent 40% of the top 200 oral drugs marketed in the United States, and more than one-third of the drugs listed in the U.S. Pharmacopeia fall into the poorly water-soluble or water-insoluble categories (Pace et al., 1999; Takagi et al., 2006; Rodriguez-Aller et al., 2015).

Interpretations of the term water-insoluble drug can vary depending on an individual’s definition. According to USP 40/NF 35, slightly soluble means that “one part of solute can be solubilized by 100 to 1000 parts of solvent.” If water is the solvent, then the water solubility of a slightly soluble drug can range from 10 mg/mL down to 1 mg/mL. If the same assumption is applied, very slightly soluble and practically insoluble or insoluble can be translated to 1 mg/mL down to 100 µg/mL, and equal to or less than 100 µg/mL, respectively. Therefore, in the broader definition, the term water-insoluble drug in this book is defined as the aqueous solubility of a drug that falls into the range of slightly soluble and below (i.e., <10 mg/mL). In the narrower definition, the term water-insoluble drug in this book indicates that the aqueous solubility of a drug belongs to the category of practically insoluble or insoluble (i.e., <100 µg/mL).

In the past two decades, with the applications of genomics, high-throughput screening, robotics, combinatorial chemistry, computational modeling, informatics, and miniaturization to the drug discovery area, far more drug candidates than ever have been generated for development (Lipper, 1999; Hann and Oprea, 2004). However, as a result of the preferred pharmacological activity process of drug discovery, which attempts to maximize the activity, biopharmaceutical or drug-like properties of new drug candidates, including water solubility, tend to suffer (Yamashita and Furubayashi, 1998; Lipinski, 2000; Caldwell et al., 2001). Although the incompatible work partnership between the preclinical groups and the discovery groups has been improved in many companies in the recent years (Alanine et al., 2003), it is noteworthy that a compound with great receptor affinity and selectivity, but with poor drug-like properties for formulation or delivery, is still rarely regarded as ineligible to enter development. This viewpoint has prevailed in industry despite the potential for a compound’s poor drug-like properties to be a major delay on the development timeline (Lipper, 1999; Kola and Landis, 2004). Compounds optimized solely on the basis of receptor-based potency, depending on the nature of the receptor, are usually hydrophobic or water insoluble. Therefore, many problems have recently been experienced in the early formulation development of drugs (Sweetana and Akers, 1996; Corswant et al., 1998; Pace et al., 1999; Di et al., 2006). Water insolubility can postpone or completely halt new drug development, and can prevent the much needed reformulation of currently marketed products (Pace et al., 1999; Caldwell et al., 2001; Hartmann et al., 2006).

Besides the newly discovered drug candidates, modification formulations of existing drugs are also gaining importance. Significant numbers of commercial insoluble drugs with improved formulations that provide for faster dissolution and enhanced bioavailability were filed as New Drug Applications (NDA) under 505(b)(2), which is relatively profitable strategy for pharmaceutical companies.

Through decades of diligent and intelligent research by pharmaceutical scientists, many techniques dealing with the formulation issues of water-insoluble drugs have been developed and accumulated in the pharmaceutical literature. A book that systematically described the techniques used for water-insoluble drug formulations could be a real benefit to development scientists. This was the primary motivation that led to the publication of Water-Insoluble Drug Formulations in 2000 and the updated second edition with additional content in 2008. During the last decade, various insoluble drug delivery technologies, especially nanoparticle-based technologies, bloomed in both academic and industrial settings, and several platforms were successfully adopted by many pharmaceutical companies. These developments have led to this updated third edition of Water-Insoluble Drug Formulations.

The aim of this book is to provide a handy reference for pharmaceutical scientists in the handling of formulation issues related to water-insoluble drugs. In addition, this book may be useful to pharmacy and chemistry undergraduate students, and to pharmaceutical and biopharmaceutical graduate students, to enhance their knowledge in the techniques of drug solubilization and dissolution enhancement. This book covers topics ranging from solubility theories, solubility prediction models, the aspects of preformulation, biopharmaceutics, pharmacokinetics, regulatory, and discovery support of water-insoluble drugs to various techniques used in developing delivery systems for water-insoluble drugs. In general, each chapter describing a solubilizing system starts with the brief theoretical background associated with the particular system, followed by practical discussions of industrial experiences, and concluded by examples or case studies.

The chapter “Solubility Theories” provides a systematic review of existing theories regarding the interactions between solutes and solvents. The chapter “Prediction of Solubility” may be helpful to those drug discovery chemists and pharmaceutical scientists who work in the discovery support area to design new drug candidates with improved aqueous solubility before they are synthesized. The chapters “Preformulation Aspects of Water-Insoluble Compounds” and “Water-Insoluble Drugs and Their Pharmacokinetic Behaviors” can be used by a formulator (especially an inexperienced one) to understand the particulars of the physicochemical, biopharmaceutical, and pharmacokinetic properties of a water-insoluble drug. When dealing with lead compounds with poor drug-like properties in early formulations, pharmaceutical scientists can refer to the chapter “Formulation Strategies and Practice Used for Drug Candidates with Water-Insoluble Properties for Toxicology, Biology, and Pharmacology Studies in Discovery Support” to obtain different formulation approaches to support the animal studies in toxicology, pharmacology, and pharmacokinetics. The chapter “Regulatory Aspects of Dissolution for Low Solubility Drug Products” provides some very useful guidelines for dissolution from the Food and Drug Administration (FDA) perspective. Some preformulation and exploratory solubilization experiments, guided by these chapters, are usually necessary before the design of a water-insoluble drug formulation.

For water-insoluble drugs with high permeability or Class II drugs in FDA’s Biopharmaceutics Classification System (BCS), drug absorption in the gastrointestinal (GI) tract is primarily limited by drug dissolution rate (Amidon et al., 1995; McGilveray, 1996; Yu et al., 2002; Pepsin et al., 2016). Therefore, the formulation work of oral solid dosage forms for Class II compounds should focus on the enhancement of dissolution rate. Dissolution rate enhancement and related techniques for the development of oral solid dosage forms can be found in the chapters “Alteration of the Solid State of the Drug Substance: Polymorphs, Solvates, and Amorphous Forms,” “Development of Solid Dispersions for Poorly Water-Soluble Drugs,” “Particle Size Reduction,” “Pharmaceutical Powder Technology—ICH (the International Conference on Harmonisation) Q8 and Building the Pyramid of Knowledge,” “Prodrugs for Improved Aqueous Solubility,” “Pharmaceutical Salts,” “Applications of Complexation in the Formulation of Insoluble Compounds,” “Liposomes in Solubilization,” “Micellization and Drug Solubility Enhancement,” and “Polymeric Micelles in Water-Insoluble Drug Delivery.”

Both dispersion and solution systems can be used to formulate oral liquid dosage forms to enhance bioavailability for water-insoluble drugs (Pouton, 1997; Yamashita and Furubayashi, 1998; Porter and Charman, 2001; Wasan, 2001). These systems can also be used to develop solubilizing systems for parenteral dosage forms to deliver water-insoluble drugs (Sweetana and Akers, 1996; Corswant et al., 1998; Pace et al., 1999; Sarker, 2005). Formulation techniques used to enhance bioavailability for oral liquid dosage forms and to solubilize water-insoluble drugs for parenteral dosage forms can be found in the chapters “Solubilization Using Cosolvent Approach,” “Micellization and Drug Solubility Enhancement,” “Polymeric Micelles in Water-Insoluble Drug Delivery,” “Liposomes in Solubilization,” “Particle Size Reduction,” “Emulsions, Microemulsions, and Lipid-Based Drug Delivery Systems for Drug Solubilization and Delivery (Parenteral and Oral Applications),” “Soft Gelatin Capsules Development,” “Prodrugs for Improved Aqueous Solubility,” and “Pharmaceutical Salts.” The chapter “Oral Modified-Release Drug Delivery for Water-Insoluble Drugs” provides a systemic review on various controlled-release technologies, which may be suitable to be used on longer-lasting applications of water-insoluble drugs. Finally, the chapter “Scalable Manufacturing of Water-Insoluble Drug Products” provides some useful discussion in process development, especially for large scale-up manufacturing of finished dosage forms of water-insoluble drugs.

In many cases in drug development, the solubility of some leads is extremely low. Fast dissolution rate of many drug delivery systems, for example, particle size reduction, may not be translated into good GI absorption. The oral absorption of these molecules is usually limited by solubility (Willmann et al., 2004; Qiu et al., 2016). In the case of solubility limited absorption, creating supersaturation in the GI fluids for this type of insoluble drugs is very critical as supersaturation may greatly improve oral absorption (Tanno et al., 2004; Shanker, 2005; Taylor and Zhang, 2016). The techniques to create the so-called supersaturation in the GI fluids may include microemulsions, emulsions, liposomes, complexations, polymeric micelles, and conventional micelles, which can be found in some chapters in the book.

There are still some drug delivery strategies under wide investigation in academic settings, including mesoporous silica particles (Latify et al., 2017), graphene oxide (Liu et al., 2008), other inorganic particles (Yue et al., 2011), all kinds of sensitive organic particles (Guo and Huang, 2014), and targeted or intracellular delivery strategies (Mitragotri et al., 2014). However, these strategies still have a long way until clinic, with lots of challenges to be figured out. The related studies are discussed in this book.

It is the authors’ hope that the concepts and techniques described in this book will lead to the development of improved dosage forms for water-insoluble drugs, and thus enhance the therapeutic advantage of this crucial class of drugs.

REFERENCES

Alanine, A., M. Nettekoven, E. Roberts, and A. W. Thomas. 2003. Lead generation—Enhancing the success of drug discovery by investing in the hit to lead process. Combinatorial Chemistry & High Throughput Screening 6: 51–66.

Amidon, G. L., H. Lennernas, V. P. Shah, and J. R. Crison. 1995. A theoretical basis for biopharmaceutic drug classification: The correlation of in vitro drug product dissolution and in vitro bioavailability. Pharmaceutical Research 12: 413–420.

Caldwell, G. W., D. M. Ritchie, J. A. Masucci, W. Hageman, and Z. Yan. 2001. The new pre-preclinical paradigm: Compound optimization in early and late phase drug discovery. Current Topics in Medicinal Chemistry 1: 353–366.

Corswant, C. V., P. Thoren, and S. Engstrom. 1998. Triglyceride-based microemulsion for intravenous administration of sparingly soluble substances. Journal of Pharmaceutical Sciences 87: 200–208.

Di, L., E. H. Kerns, S. Q. Li, and S. L. Petusky. 2006. High throughput microsomal stability assay for insoluble compounds. International Journal of Pharmaceutics 317: 54–60.

Guo, S. and L. Huang. 2014. Nanoparticles containing insoluble drug for cancer therapy. Biotechnology Advances 32(4): 778–788.

Hann, M. M. and T. I. Oprea. 2004. Pursuing the leadlikeness concept in pharmaceutical research. Current Opinion in Chemical Biology 8: 255–263.

Hartmann, T., J. Schmitt, C. Röhring, D. Nimptsch, J. Noller, and C. Mohr. 2006. ADME related profiling in 96 and 384 well plate format—A novel and robust HT-assay for the determination of lipophilicity and serum albumin binding. Current Drug Delivery 3: 181–192.

Kalepu, S. and V. Nekkanti. 2015. Insoluble drug delivery strategies: Review of recent advances and business prospects. Acta Pharmaceutica Sinica B 5(5): 442–453.

Kerns, E. H. and L. Di. 2003. Pharmaceutical profiling in drug discovery. Drug Discovery Today 8: 316–323.

Kola, I. and J. Landis. 2004. Can the pharmaceutical industry reduce attrition rates? Nature Reviews Drug Discovery 3: 711–715.

Latify, L., S. Sohrabnezhad, and M. Hadavi. 2017. Mesoporous silica as a support for poorly soluble drug: Influence of pH and amino group on the drug release. Microporous and Mesoporous Materials 250: 148–157.

Lipinski, C. A. 2000. Drug-like properties and the causes of poor solubility and poor permeability. Journal of Pharmaceutical and Toxicological Methods 44: 235–249.

Lipper, R. A. 1999. E. pluribus product. Modern Drug Discovery 2: 55–60.

Liu, Z., J. T. Robinson, X. Sun, and H. Dai. 2008. PEGylated nanographene oxide for delivery of water-insoluble cancer drugs. Journal of the American Chemical Society 130(33): 10876–10877.

McGilveray, I. J. 1996. Overview of workshop: In vitro dissolution of immediate release dosage forms: Development of in vivo relevance and quality control issues. Drug Information Journal 30: 1029–1037.

Mitragotri, S., P. A. Burke, and R. Langer. 2014. Overcoming the challenges in administering biopharmaceuticals: Formula...